This circuit was found in a Popular Electronics from the 90s. It is based on components still common today and an optical coupler for the triac. The sensor is a thermistor.
Using the NE5205 integrated circuit this circuit was found in the May 1987 issue of Radio...
This circuit was found in a 1980s American schematic. Transistors can be modern equivalents. The...
This circuit is from a 1972 Motorola publication. The used transistor can still be found, but it...